Add Zastava M21, M76 and Sa vz. 61 Scorpion magwells

Added missing magwells based on RHS GREF and SAF weapons.

addons/jam/CfgMagazineWells.hpp

@@ -36,6 +36,7 @@ class CfgMagazineWells {
     #include "magwells_762x25.hpp"      // 7.62x25mm Tokarev
     #include "magwells_762x38R.hpp"     // 7.62x38mmR | 7.62 mm Nagant
     #include "magwells_763x25.hpp"      // 7.63x25mm Mauser | .30 Mauser Automatic
+    #include "magwells_765x17.hpp"      // 7.65x17mm
     #include "magwells_765x21.hpp"      // 7.65x21mm Parabellum | 7,65 Parabellum | 7.65mm Luger | .30 Luger
     #include "magwells_8x22.hpp"        // 8x22mm Nambu
     #include "magwells_9x18.hpp"        // 9x18mm Makarov | 9mm Makarov | 9x18mm PM

addons/jam/magwells_556x45.hpp

@@ -3,6 +3,7 @@
     class CBA_556x45_FAMAS {};          // FAMAS F1
     class CBA_556x45_G36 {};            // H&K G36
     class CBA_556x45_HK33 {};           // H&K 33/53/93
+    class CBA_556x45_M21 {};            // Zastava M21
 
     class CBA_556x45_MINIMI {
         BI_boxes[] = {

addons/jam/magwells_765x17.hpp

@@ -0,0 +1 @@
+    class CBA_765x17_VZ61 {};      // Sa vz. 61 Scorpion

addons/jam/magwells_792x57.hpp

@@ -2,5 +2,6 @@
     class CBA_792x57_G43 {};        // G43, G41
     class CBA_792x57_K98 {};        // K98, G98
     class CBA_792x57_LINKS {};      // MG42, MG34
+    class CBA_792x57_M76 {};        // Zastava M76
     class CBA_792x57_MG08 {};       // MG08
     class CBA_792x57_TROMMEL {};    // MG34 Patronentrommel 34